1. Field of the Invention
The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus that allows recording at a high speed to a recording medium with a plurality of widths using a recording head in which a plurality of image-recording elements are arrayed, and that enables restoration of defective pixels.
2. Description of the Related Art
A known example of an image recording apparatus is an inkjet printer that has an inkjet head (recording head) in which a plurality of nozzles (image-recording elements) are arrayed, and that forms images on a recording medium by discharging ink from the nozzles as the recording head and recording medium are moved relative to each other.
When attempting to obtain a high-quality print in such an inkjet printer, the droplet diameter during ink discharge is preferably made small, and the space between neighboring ink droplets discharged to the surface of the recording medium is preferably made narrower, but the diameter of an ink discharge port is even smaller than the droplet diameter during ink discharge, and the space between neighboring ink discharge ports has substantially reached a limit in terms of ensuring machining accuracy.
Known inventions (Japanese Patent Application Publication No. 2002-1936, for example) devised in response to this problem are designed such that an inkjet head is rotated within the plane parallel to the conveyance plane of the recoding medium, the inkjet head is rotated by a predetermined angle with respect to the conveyance direction, the interval between the ink discharge ports in the inkjet head is reduced in the conveyance direction of the recording medium, and the pixel density in the print is increased by a corresponding amount to obtain a high-quality print.
In the above inkjet printer, ink may not be discharged or discharged ink may not have a proper flight direction due to clogged nozzles in the print head, a soiled meniscus surface on the ink, or other factors, and missing spots may occur during printing for this reason. Such missing spots in printing hardly stand out due to the considerable overlap in the shuttle-scan method, but print defect nonuniformity is marked in the case of a line head.
Known inventions developed in response to this problem include those (Japanese Patent Application Publication No. 11-334047, for example) that have a device for detecting nozzle defects in a line inkjet printer with an inkjet head in which a plurality of nozzles are arrayed with a length corresponding to the width of the recording medium, and that retouch defective pixels when there are defects in the line head nozzles by recording images using an auxiliary head jointly provided to the line head; those related to an image recording apparatus for recording images with the dot matrix method (Japanese Patent Application Publication No. 9-24627, for example) in which the direction of the recorded recording medium is reversed while the medium is moved by a predetermined amount with respect to the recording head in the width direction, and when a printing defect is found, the printing defect is retouched so that dot data to be printed is printed using a normally functioning dot print element at a predetermined distance from the defective dot print element when the recorded recording medium is discharged; and other inventions.
Nevertheless, as cited in Japanese Patent Application Publication No. 2002-1936 above, when the recording head is rotated by a predetermined angle to record images, the apparent image density is increased and a high-quality print can be obtained, but there are drawbacks in that the recording area in the width direction of the recording medium becomes narrow, the processing speed decreases when an attempt is made to record with high quality to a recording medium with a broad width, and the processing speed cannot be increased or the productivity improved when images are recorded with high quality to a narrow recording medium.
In the invention cited in Japanese Patent Application Publication No. 11-334047, there are drawbacks in that the apparatus configuration has considerable redundancy because a compensating auxiliary head must be jointly provided for each color in addition to a regular line head. In the invention cited in Japanese Patent Application Publication No. 9-24627, the direction of the once printed recorded paper is reversed, print defects are detected, and a determination is made as to whether to reprint, so regardless of the presence of a print defect, the recording paper always reciprocates through the print head, and productivity is poor. Furthermore, only a normally functioning dot print element disposed at a predetermined distance from the defective dot print elements is used for printing, bringing about a drawback whereby the print defects are not necessarily completely retouched due to the skewing or other effect of the recording paper.